CA1158144A

CA1158144A - Spun fleece possessing great dimensional stability and a process for producing it

Info

Publication number: CA1158144A
Application number: CA000352870A
Authority: CA
Inventors: Ludwig Hartmann
Original assignee: Carl Freudenberg KG
Current assignee: Carl Freudenberg KG
Priority date: 1979-06-01
Filing date: 1980-05-28
Publication date: 1983-12-06
Also published as: JPS55163253A; ATA288680A; DE2922427C2; GB2053301A; BE882804A; NL8003154A; CH638361GA3; US4363845A; JPS6229541B2; FR2457919B1; NL187983B; DE2922427A1; FR2457919A1; NL187983C; AT384833B; GB2053301B; MX154221A; CH638361B

Abstract

ABSTRACT OF THE DISCLOSURE
A spun fleece is disclosed which consists of several layers of randomly-laid filaments superimposed on each other, and which are joined to each other, characterized by a mixture of single filaments and filament groups, wherein the single filaments and the filament groups are mutually bonded at least at their cross-over points, the filament groups being multi-filament strands consisting of single filaments in which the single filaments are at least in part arranged parallel to each other, and either partially or completely bonded to each other. A process for production of the spun fleece is also disclosed.

Description

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A SPUN FLEECE POSSESSING G~EA~ DIMENSIONAL STABILITY AND
-A PROCESS FOR PRODUCING IT
The invention relates to a spun fleece or non-woven textile consisting of several layers of randomly displaced fila-ments, these layers being positioned one on top of the other and being bonded together. A special arrangement of the fibres provides features that were formerly impossible to achieve, in particular great dimensional stability and an especially favorable modulus.
Spun fleeces are familiar. Their use as carrier materials for plastic coating forms part of the state of the art. Primarily, polyamide and polypropylene spun fleeces having weights per unit area of 40 to 120 g/m2 are used for coating with conventional PVC
or polyurethane. Thicker and heavier carrier fleeces can also be produced, preferably of needled staple fibres and these are pro-cessed, for example, into porous (poromeric) artificial leathers.
Most of these carrier materials are used to manufacture layered artificial leather that finds application in the purse and luggage industry, in shoe manufacture, for clothing and for furniture.
Fleeces of these types are not suitable for processing that involves great stretching loads.
Spun fleece carrier materials for use in the tufting field are described in DE-PS 22 40 437, wherein mention is 1 1~8144 made of the fact that highly stable spun fleeces of this type are preferably anchored by autogenous, i.e., fibre bonding.
Spun fleeces that are produced in this way have proven to be highly satisfactory as dimensionally stable carrier materials for the production of tufted carpeting. Polyester fleeces that are bonded with copolyester fibres are, however, extremely porous and have an open structure in order to facilitate penetration of the tufting needles.

However, in many cases highly porous fleeces of this kind are not desirable and a number of new coating products require the smoothest possible carrier materials with a closed surface, and these require ever greater stability, stronger retention, and very hiyh moduli at high temperatures. In particular, carriers with high moduli are required for coating with bitumen for roofing materials, and with PVC for relieved floor coverings (cushioned vinyl). The highly technical processing requires great tensile forces of in excess of 800 Newton/5cm strips with a maximum elongation of less than 60% and a minimum width shrinkage of less than 100 mm at a coating temperature of 200C and 4 m strip width.

Neither conventional fleeces of staple fibres nor already familiar spun fleeces have been able to meet the requirement outlined above. In particular, the temperature dependability of the modulus is unsatisfactory in every case, because, with increasing temperatures, extremely marked changes to higher values take place and this results in greater elongation and/or deformations. This applies to spun fleeces that are bonded both with binding fibres and with dlsperslons .

The invention undertakes the task of developing a fleece material which does not have the aforementioned disadvantages and which, in addition, displays great dimensional stability and very high moduli at higher temperatures.

As provided for by the invention, this task is solved by using a multi-filament spun fleece, in which a large number of filament groups is mixed together and in which there are individual filaments that are bonded to the filament groups, at east at the points of intersection, in which connection secondary bonding agents are preferred. In addition, a particularly favourable process for the production o~ spun fleeces of this type is also proposed.

The spun fleece according to the invention is a mixed fleece consisting of randomly distributed individual filaments mixed with multi-filament strands produced with the help of secondary bonding systems. A secondary bonding system as discussed herein is understood to mean high-polymer bonding substances that are not spun like the bonding fibres, but are incorporated after the primary spinning process.

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The present invention provides a spun fleece consisting of several layers of randomly-laid filaments superimposed on each other, and which are joined to each other, characterized by a mixture of single filaments and filament groups, wherein the single filaments and the filament groups are mutually bonded at least at their cross-over points, the filament groups being multi-filament strands consisting of single filaments in which the single filaments are at least in part arranged parallel to each other and either partially or completely bonded to each other.

The invention further provides a process for making spun fleeces according to the invention which is characterized in that parallel strings of threads are spun from a number of spinning nozzles arranged adjacent to each other and the thread strings are aerodynamically stretched and laid flat on top of each other, whereby a mixed fleece of single filaments and filament groups is formed by a suitable aperture configuration of the spinning nozzles, whereby the single filaments of the filament groups are bonded into heterogeneous multi-filaments by means of secondary bonding agents, at least over part of their length in their mutually parallel position, and the multi-filaments and the single filaments are mixed in a random lay and bonded mutually, at least at their cross-over points.

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US Patent 3,554,854 describes spun fleeces produced from parallel groups of filaments, in which the filament groups are guided along parallel paths from the spinning nozzles to the capture zone and thereby layered flat on top of each othe~. The individual filaments forming the filament groups are not bonded into their parallel configuration with the help of secondary bonding agents; the whole fleece is subjected to a bonding process at the cross-over points.
I'hus, there is no build-up of a mixed fleece of multifilaments and individual filaments in superimposed layers. The filament groups are in flat layers. This flat layering distinguishes the filament-group fleecè from the wrinkled and bulky mats such as are produced from glass-fibre strands, for example, in US Patent 2,736!676. It has been shown that the glass-fibre strands according to the process in US Patent 2,736,676 display excessive extension under tensile loads as a result of the arc shaped laying pattern and the resulting deficient cohesion of the individual filaments, with the result that they cannot be used for dimensionally stable spun fleeces.

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1~581~4 The characteristics of the spun fleece according to the present invention are considerably better than those of the spun fleece just described. First, it is distinguished from the one according to US Patent 2,736,676 by greatly improved dimensional stability. However, it is also far better than the spun fleece described in US Patent 3,554,854 because the filament groups or multifilaments are mixed with individual filaments and the filament groups are not autogenous, but are bonded to each other with the help of secondary bonding substances, which results in the so-called multifilaments.
The individual filaments serve to stabilize the total mixed fleece, e,g., as bonding filaments with a low softening point, to provide for bonding at the cross-over points.

According to the invention, the filament groups remain flat, e~g., they do not form arcs or curls, as are seen, for example, in US Patent 2,736,676. The filament groups can consist of a mixture of various individual filaments, e.g., of thermoplastic filaments of various polymers bonded by elastomers or duromers.

According to the invention, an especially favourable process for the production of the mixed fleeces is also provided, whereby the spun fleeces of mixed individual fleeces are built up of parallel filament groups that are disposed in layers one on top of the other, thereby producing 11~8144 a random layer of filament groups made up of various numbers of filaments, and the individual filaments within the group are bonded into joined multifilaments with the help oE
secondary bonding substances, at least lengthwise along their parallel layers.

The flat superimposition of layers of combined filament groups, i.e., multifilaments of different numbers of filaments, mixed with random-laid single filaments, results in great firmness as a result of the filament groups or joined multifilaments that are present, whereas the single filaments that are dispersed therein as bonding media serve to stabilise the area bonding, either because they serve as binding fibres as a result of a lower softening point, or because they function as bonding media when secondary bonding agents are applied, è.g , in the form of dispersions, because they are free laid and because of their large area.

An important advantage of the mixed fleece structure of multifilament groups and single filaments according to the invention lies in the variation of pore size of the spun fleece. This makes it especially suitable for carrier material that is subjected to great loads. Thus, for example, with no difficulty it is possible to use the mixed fleece as roofing material if is is processed with bitumen.

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-1 1S814~ -In order to prevent the penetration of water (capillary effect) into the prepared roofing strip it is necessary to arrange for a specific pore size in the fleece, in order that complete penetration is achieved when the fleece is immersed in bitumen. Since, on the other hand, a prescribed weight per unit area by fibre is necessary in order to achieve the required rigidity (e.g., 200 g/m2 polyester filaments), the pore size can be varied when using the structure consisting of multifilament groups mixed with single filaments. ThiS variation of pore size is also essential when processing involves bitumen immersion mixtures of different viscosities. If the spun fleece is built up of only conventional single filaments, at the given weight per unit area (200 g/m2 as in the aforementioned example) the pore count and the size of the pores are both considerably smaller than in the case of the structure of a fleece of the same weight, consisting of multifilament strands consisting of, for example, six groups, i e., a multifilament of six single filaments, since the single filaments that make up the group are parallel and close together, and, because of the random lay of the groups, form much larger pores. By using the structure of a mixed fleece of specific percentages of multifilament groups with single filaments, it is possible to prepare a suitable carrier material with the maximum impregnation according to the viscosity of the bitumen, for the weight per unit area in question.

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The importance of the filaments that are bonded into groups along their parallel set can be explained on the basis of the spun-fleece methodology of aerodynamic stretching. As is known, in the spun-fleece process, the filaments are stretched out of the spinning nozzles with the help of fast-moving streams of air. The molecular orientation that occurs when the molten and hot monofilaments are pinched must be "frozen" as rapidly as possible, i.e., the temperature of the fibers must be reduced to a point below the glass transition point or the recrystallization temperature.
Naturally, this process takes place best in the case of a fibre with a suitably large surface area. Now, however, for extremely rigid spun fleeces for technical applications the thickest and most rigid possible filaments are required;
these are extremely difficult to produce by the aerodynamic spun-fleece process because of the aforementioned rates of heat loss required to achieve the maximum molecular orientation. According to the present invention these difficulties are overcome because of the fact that relatively thin filaments that are readily amenable to aerodynamic stretching are spun in the form of groups, in which connection cooling proceeds well because of the separation of the single filaments in the groups during the spinning process, thereby providing maximum molecular orientation and thus the maximum rigidity; after the goups have been formed into a fleece, these single filaments within the groups are 11S814~
joined into strands or multifilaments with the help of secondary bonding substances. Thus, a spun fleece that displays maximum rigidity values is obtained, since it behaves as if built up of very thick and extremely rigid threads or bristles. Very fine threads result in especially soft spun fleeces; coarse threads result in harder spun fleeces. A harder and stiffer spun fleece is required for many applications, e.g., for producing carrier materials used with bitumen, such as is used for roofing products or for road reconstruction or bitumen-layer reinforcement in a road surface.

The single filaments are spun and the mnltifilaments are formed in two steps of the process and this offers major advantages, as will be described below. After consolidation of the fleece, i.e., after the mutual bonding of the filament groups or single filaments, the flat, i.e., not curled or arced, superimposition of the filament groups or multifilaments together with single filaments to form a multifilament fleece results in extremely low expansion under load and a high modulus, even at higher temperatures. A
specific quantlty of single filaments will be obtained as a result of separation of the initially loose filament groups, or else they will be spun on, as will be described to follow.
The rigidity profile of the spun fleece can be varied greatly by varying the proportions of multifilaments to single 1 1581~

filaments. When producing roofing strip, not only are tensile strength, tear resistance, and tear-creep resistance important: nail retention and puncture resistance are also important. It has been shown that optimal tensile strength does not go hand-in-hand with optimal tear-creep resistance, because in the latter instance it is important to distribute the force strain over a large area. This, in its turn, can be greatly influenced by the number of filaments or multifilament groups. Here, too, a suitable number or mixture makes optimization to every requirement profile possible. In the same way, the extensibility and elasticity can be varied very greatly by this controlled mix, in which connection it must be noted that for the practical use of these carrier fleeces, i.e., for the production of roofi~g material, this represents considerable technical progress. Conventional roofing strip material, e.g., of glass fibre mat, permits no adjustment of extensibility or of elasticity, and as a result constant tearing occurs with the extension that takes place in conventional flat roofs. This also applies when these materials are used to fill gaps in bitumen road surfaces.
Here, the spun fleeces according to the present invention have excelled in that they stop cracks and shifts coming from the lower levels and keep the bitumen surface (e.g., application thickness 6 cm above the spun fleece) free of cracks. Great variations in elasticity can be achieved by varying the proportion of multifilaments to single filaments.

1~583L44 In the drawings:
Fig. 1 is an isometric view of apparatus used to produce the multi-filament spun fleece according to the invention;
Fig. 2 is a diagrammatic plan view of a spinning beam of the apparatus of Fig. 1, showing aperture configurations;
Fig. 3 is a diagrammatic view of a multi-filament strand bonded intermittently;
Fig. 4 is a diagrammatic view of apparatus for inter-mittent bonding of filament groups to form a multi-filament strand;
Fig. 5 is a diagrammatic view of a cross-section of filament layers of a spun fleece according to th~ invention;
Fig. 6 is a diagrammatic plan view of a spun fleece according to the invention; and Figs. 7 and 8 are photomicrographs of a spun fleece according to the invention.

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Figure 1 shows a system used to produce the multi-filament spun fleece according to the invention. The letters A and B indicate longitudinal spinning nozzles in an alternating arrangement, in which connection the aperture configuration of the nozzles marked A differs from that of the jets marked B. The differences in the aperture configurations are shown in greater detail in Figure 2. In each instance, the nozzles are located on a so-called spinning beam; Figure 1 shows three such spinning beams, lettered C, D, and E, arranged one behind the other. The bunches of filaments or filament groups that emerge from the spinning beams are guided with the help of air jets into the guide channels N on a parallel path towards the collector belt F and the underlying suction stage H;- at the points of contact O they are random-laid into a superimposed multi-filament/single filament mixed fleece G. After leaving the collector belt the fleece is bonded thermally or compressed by a calender with heated rollers J. Finally, it is impregnated with a dispersion, e.g., a modified polyacrylate, in the foulard roller K. When this is done, the parallel multifilament groups are joined to each other, and to the single filaments at the cross-over points. The impregnated fleece is dried with a drum drier L and rolled up at M.

Figure 2 provides a plan view of a portion of the underside of a spinning beam D, and shows three different ~. .

1158-14'1 nozzles A, B, and B' in an alternating arrangement. These nozzles A, B, and B' differ from each other in the configuration of their apertures, A being a three-fold combination of spinning apertures that results in three-fold filament groups. The B nozzles are a simple row of apertures which, for the most part, generate a number of single filaments, whereas the B' nozæles have in each case two rows of apertures arranged in twos that result in the so-called twinned filaments. In each case, the multifilament fleece can be structured in a different way by any configuration of the apertures with other arrangements of the aperture groups.

Mixed fleeces of different types of multifilament groups can be built up by using other aperture configurations for adjacent nozzles, or by providing a spinning beam with nozzles of only one aperture configuration but arranging the adjacent spinning beam with another aperture configuration.
The multifilament can be mixed with single filaments, in that nozzles with suitable aperture configurations are incorporated as is shown in Figure 2.

Superimposition can also be effected in that, for example, the spinning beam D spins, in the main, parallel groups of, for example, six filament, while the adjacent beam, E, spins mainly single filaments, or vice versa. In each case, because of the running direction of the newly 1 ~58~
formed spun fleece towards the calender or the drier and take-up roller the fleece that is procluced by the spinning beams that are arranged one behind the other will be superimposed in ]ayers, so that spinning beam D will spin onto the fleece generated by spinning beam C, and so on. By this means it will be possible to achieve multifilament superimposition, if this is desired, i.e, the fleece of superimposed single layers can be varied with regard to the single layers. This variation can result from the filament grouping, or from the physical or chemical nature of the polymers that are to be spun. This means that the different spinning nozzles A or B can spin different kinds of polymers, in exactly the same way that the different spinning beams can spin different polymers so that one achieves a spun fleece that is built up from different layers, and this can be consolidated into a multifilament spun fleece by the calender J or impregnation at K. In this regard, it is important that there are no curled or arced layers through the thickness of the fleece, caused by spinning flat multifilament layers one on top of the other, because this will result in excessive expansibility of the finished product when it is subjected to tensile loads. This is illustrated in the schematic sketches of the fleece structure shown in Figs. 5 and 6.

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The followin~ are examples of the base materials for the different types of spinning polymers: poly-amide, polyester, polypropylene, polyethylene, and coploymers of these substances. The following physical variables can be considered: various filament thicknesses, various filament cross-sections, (e.g., round and oval), various degrees of crystallization, various softening points, etc. All of these variables, or only a few of them, can be present in a multifilament fleece. However, the multifialment fleece can consist of one and the same substance and be built up with one and the same physical characteristics and yet still be characterized by the fact that it contains various types of - filament aggregates, i.e., it may contain single filaments, double filament groups, groups of three, etc. These various types of groupings can be combined flat with each other in a random lay in one layer; however, they can also be arranged in differentiated layers one above the other, according to whether they have been spun from alternating spinning nozzles in a beam or from different beams with different types of nozzles. The bundles of thread from one beam are usually mixed with each other by back and forth motion, e.g., by exploiting the Coanda effect, so that the threads from adjacent nozzles A and B will be adequately mixed.

The multifilament fleece according to the invention is hardened in one process of the three-stage stiffening, so .

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that considerable progress has been achieved vis-à-vis the state of the art. In this three-stage stiffening, these threads or multifilament yroups are first lightly pre-hardened autogenically by the application of heat and pressure, whereby, for example, the monofilaments are used as bonding filaments because of a lower softening temperature, because of either chemical or physical modification. This pre-bonding serves to stabilise the whole fleece strip and make it easier to handle it. Then, in a second stage, the threads in the interior of the fleece strip are hardened by the application of dispersions, so that the bonding media bond the single filaments of the filament groups in their parallel position to the multifilament strands. In a third stage of the stiffening process the spun fleeces are bonded at the cross-over points, dried, and then condensed at high temperature. This three-stage bonding process results in a structure that is highly differentiated with regard to the temperature slope of the modulus, with regard to density and surface smoothness, as well as to thickness that is, however, eminently suitable for use as a dimensionally stable carrier material for high temperature applications. When this is done, as has been discussed, adhesion of the single filaments within the parallel groups into multifilament strands is achieved. This structure is shown in greater detail in Figures 5 and 6. In special cases, the hardening in the second and third hardening stages can be combined.

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The build up of the spun fleeces according to the invention from filament groups, mixed with single filaments, can, as already discussed, be used to great advantage from the point of view of process technology if, for example, the single filaments are used as bonding fibres, insofar as they are produced from polymers having a low softening point.
Thus, for example, the single filaments that form the groups or subsequent multifilaments can be built up from polyethylene terephthalate, while the bonding filaments are built up from polyethylene terephthalate-co-isophthalate. In the calendering process J shown in Figure 1 these bonding filaments are activated and finally the polyester filaments that form the filament groups are cemented into multi-filaments in the impregnation process K. ~owever, the single filaments can also be adjusted for this purpose by physical variables, e.g., a smaller degree of elongation.

It has already been stated that a flat stratum without pronounced curling, i.e,, without long arcs, is valued for the ; production of the very rigid spun fleeces according to the invention, since with an arc-shaped stratum excessive elongation occurs under load. The filament groups that are cemented into multifilaments that build up the fleece are heterogeneous multifilaments that cannot be spun in a spinning process as heterofilaments, but which are bonded into heterogeneous multifilaments in a stage of the process that is distinct from the spinning process. This entails the great advantage that heterogeneous multifilaments or heterofilaments can also be built up in proportion from such substances as cannot be spun. In addition to thermoplastics, elastomers and duromers or duroplastics can also be used to produce multifilaments. For example, a multifilament of six polyester filaments (titer 12 dtex) is bonded into a multifilament with the help of a polyacrylic ester or a melamine-formaldehyde resin. Or a multifilament spun fleece can be built up, for example, from three single filaments of an aromatic polyamide bonded with an epoxy resin into a multifilament fleece that is resistant to high temperatures.
An extremely tough multifilament fleece can be built up from groups of polypropylene filaments bonded into a multifilament fleece with the help of polybutadiene-acrylonitrile elastomers. The combination of polyester filaments bonded with the help of duromers, e g., melamine/formaldehyde resins, combined if necessary with polyacrylic esters, into multifilament fleeces is of importance, especially for the production of carrier materials for roofing strip or for bitumen-road construction because it results in a surface structure of great dimensional stability that is deformed very little by heat. Above all, great dimensional stability under various climatic conditions is achieved thereby, as is always demanded by the construction sector but which, up to - .

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now, has not been achieved. In this regard, the present invention represents considerable technical progress.

The multifilaments do not have to be present in the form of continuously cemented strands; the single filaments that make up the multifilaments can be cemented into multifilaments in sections. It has been shown that in many cases cementing in sections, as is shown in Figure 3, will be sufficient to achieve optimum characteristics, and closer examination of the fleece structure will render this comprehensible.

The total fleece, like all other fleece material, is bonded because the fibres are cemented at the crossover points, either by bonding fibres or wi-th the help of secondary bonding media,- e.g., in the form of bonding dispersions or powder. The fleece strip is thus stabilised by fixed bonding points or areas at the crossover points and it is sufficient that in each instance the multifilaments are cemented at such lengths as are provided by the number of crossover points.

Since for practical purposes the multifilament fleece is mixed with single filaments, this results in specific lengths of the filament groups multifilament structure, i.e., single filaments bonded together parallel, in other places separate 11581~

single filaments that are in part parallel that can in certain areas separate into single filaments and in other places converge again.

It has been shown that this structure entails great advantages as far as production characteristics are concerned, For example, when building up a multifilament fleece of polyester filaments, that are bonded into a multifilament with melamine-formaldehyde resin, excessive rigidity of the end product resulted as a result of completely cementing the whole length of the single filaments. If parallel cementing is carried out only in certain places (as is shown schematically in Figure 3), there ; are flexible areas that function like joints, and the total fleece is tougher and more elastic. The characteristics of the multifilament fleecè can be varied by variation of the multifilament stretches to the unbonded parallel filament ` stretches. For example, there is a marked increase in tear `~ creep resistance or stitch tear resistance (resistance to stitches tearing out) if there are sufficient such joints in `- 20 the fleece strip. The percentage of filament stretches to multifilament can be controlled by the impregnation process at K
in Fiqure 1, by varying the concentration of the bonding medium or its absorption, since it has been shown that as a result of surface tension the bonding medium has a tendency to collect between those filaments of the group that are ~ , 1~5814~

closest together. Control can be exercised by variation of the proportions by weight or the number of filaments in the groups to the proportion by weight of the bonding substance.
By "puffing up" the paralleled filaments at specific points or on specific stretches the endless filaments run out from the cemented multifilament strands and form a so-called joint, only to be recemented into the multifilament strand further on.

The sector-wise cementing of the filament groups into multifilament strands can also be effected in that before entering the thread guide channels, the filament groups pass over coating rollers (Figure 4~ that apply intermittent bonding, so that an intermittently cemented multifilament as in Figure 3 results. The coating rollers for the intermittent bonding application are coated intermittently by a coating systemt that is not shown in the drawings; the coating rollers then apply this intermittent bonding to the filament groups.

s Figure 6 is a plan view of a spun fleece according to the invention that is in the form of a mixed fleece consisting of single filaments and multifilaments. The single filaments are lettered a; the letter b indicates two-fold groups; c indicates three-fold groups; the : crcss-over points of the multifilaments are lettered e, and d 1~8144 indicates the cross-over points from single filaments to multifilaments. As has been discussed above, in many cases it is advantageous, although not essential, to use the filaments marked a as bonding filaments. The hatched areas between the single filaments indicate the secondary bonding material that bonds the filaments of the groups to multifilaments, e.g., melamine resin areas to polyester filaments.

By way of example, the filaments that make up the filament groups b and c can be built up from polyethylene terephthalate having a high degree of extensibili~y, whereas the single filaments a are built up from polyethylene terephthalate of low extensibility or from polyethylene terephthalate-co-adipate. The hatched areas can also consist of a modified trimethylol melamine resin modified polyacrylic acid ester, as is described to follow in a preferred version.

Figure 7 of the drawings is a photomicrograph of a spun fleece of this type, taken with a ~aster electron microscope at a magnification of 50:1, wherein a multifilament fleece having five-fold groups, two-fold groups, and single filaments can be plainly seen.

In many applications, the fleece is bonded at the cross-over points with the same bonding system that forms the ` `~ .~, ~ '' ' ' :

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multifilament strands. Figure 8 is a photomicrograph of a bondinq point of this kind; this photograph was taken from a Raster electron microscope at a magnification of 220:1. A multifilament of a three-fold group can be plainly seen.

Example A spinning installation that has spinning nozzles A and B in an alternating arrangement over a fleece width of 5 m as shown in Figure 1 is used to produce a spun fleece according to the invention. The spinning nozzles A have four rows of spinning apertures with a capillary diameter of 0.3 mm in the ;~ fifth and second groupings alternately. The A spinning nozzles are fed with polyethylene terephthalate at a melting temperature of 290C, at the ra~e of 5 ~/aperture/minute. The ~'! ' B nozzles are fed with polyethylene terephthalate-co-adipate at the rate of 2.7 g/aperture/minute at a melting temperature of 270C.

The groups of threads or threads that are formed by the spinning nozzles are exposed to cold air at a temperature of 38C, that is injected at right-angles to the direction of thread movement for a distance of 150 mm, and are then passed--in the form of parallel-laid thread strings--to an aerodynamic extraction section. The thread groups are accelerated to an extraction velocity of 5,000 m per minute, 1 1~814ll with the help of coanda rollers with a frequency of 675 strokes moved back and forth and then deposited in flat layers on a sieve band having a suction system beneath it;
this takes place at a rate of 10 m/spinning beam, i.e., with three spinning beams the resulting rate is 30 m.

Next, the fleece is pre-stiffened on a 6-m wide heated calender at a temperature of 95. The pre-stiffened fleece is impregnated with a bonding medium dispersion of a copolymerisate of 30% styrene, 40% butyl acrylate, 20% acrylonitrile and 5~ each of methylolated acrylamide and methacrylic acid with the use of an anionic surfactant, whereupon the filamènt groups are cemented into multifilament strands (absorption 10% dry).
The fleece is then impregnated in a second impregnation tank, using a mixture of a methylolated melamine/formaldehyde precondensate with the aforementioned poly-acryl ester in the proportion of 3:7 and with a total bonding agent absorption of 30~ in relation to fibre weight. The fleece is dried using a drum drier at a temperature of 100 and then condensed at 130. The final weight of the multifilament fleece is 230 g/qm.

It has been shown, especially, that a combination of multifilament groups of, in each case, several polyester filaments bonded with polybutyl acrylate/melamine resin is best suited for the production of highly rigid carrier , ~, 11S8~44 materials for roofing material, in which connection it has been shown that an especially high interlacing and thereby formation of the filament groups to multifilament groups is achieved in the combination of available methylolated melamine resin. Trimethylol-melamine resin can be replaced, either in part or completely, by a polymerized methylol acrylamide (CH2 = CH-CO-NR2).For this reason, in the e~ample, a combination both with and without methylolated melamine resin is shown. Although the polymerized acrylo-nitrile provides no interlacing it does reduce the glasstemperature of the film, thus improving adhesion of the bonding film to the filament groups. Especially good adhesion to the polyester filaments in the groups, i.e., in bonding of the multifilaments strands and especially good interlacing is provided by those that contain the reactive -COOH and -OH groups. Because of its softness, the butyl-acrylate results in good adhesion; the interlacing groups then reduce this softness on condensation, and result in an end product with a high modulus, particularly at high temperatures.

An especially preferred varlation according to the invention is represented by a spun fleece of polyester filament groups bonded with polybutyl acrylate copolymer.s to heterogeneous multi-filament strands, which are then interlaced with the help of carboxyl- and N-methylol groups.

' The preferred filament thickness is between 6 and 15 dtex, with a circular cross-section and a softening point above 150C, whereupon the modulus, measured over a width of 5 cm, is adjusted as follows:

At 3% stretch 270 Newton At 5% stretch 315 Newton At 10% stretch 380 Newton It has been shown that the interlacing of the strands must be carried out during careful increase of temperature, and it is for this reason that in the example pre-drying is first carried out at 100C and final condensation completed ~ at 150C. By this means it is possible to achieve optimum : interlacing between the various components. If the temperature is increased too rapidly each component will interlace on its own, and no optimum modulus or strength of the multifilament strands or of the spun fleece produced from them will be achieved.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A non-woven textile consisting of several layers of randomly-laid uncrimped filaments flatly superimposed on each other, and which are joined to each other, characterized by a mixture of single filaments and filament groups, wherein the single filaments and the filament groups are mutually bonded at least at their cross-over points, the filament groups being multi-filament strands consisting of single filaments in which the single filaments are at least in part arranged parallel to each other, and either partially or completely bonded to each other.

2. A non-woven textile according to claim 1, further characterized by heterogeneous multi-filament strands consisting of single filaments of different chemical composition and/or physical characteristics and/or shape.

3. A non-woven textile according to claim 1, further characterized in that the filament groups are bonded to each other and/or the filament groups are bonded to the single filaments with one or several bonding media.

4. A non-woven textile according to any one of claims 1 to 3, further characterized by filament groups that consist of heterogeneous multi-filament strands of polyester filaments that are bonded to parallel strands with the help of bonding media that are cross-linked with methylol groups.

5. A non-woven textile according to any one of claims 1 to 3, further characterized in that the heterogeneous multi-filament strands consist of polyethylene terephthalate filaments bonded to each other to form strands that are at least in part parallel to each other by the use of polybutyl acrylate as bond-ing media, and which contain N-methylol-modified monomers in the form of copolymers.

6. A non-woven textile according to claim 1, further characterized in that at least the filament groups are laid flat.

7. A non-woven textile according to any one of claims 1 to 3, further characterized in that single filaments and filament groups are present in the proportion of two to one.

8. A non-woven textile according to any one of claims 1 to 3, further characterized in that the filament groups consist of a mixture of thermoplastic single filaments that are bonded into multi-filaments with thermoplastics, elastomers or duromers.

9. A process for the production of non-woven textiles characterized in that parallel strings of threads are spun from a number of spinning nozzles arranged adjacent to each other and the thread strings are aerodynamically stretched and laid flat on top of each other, whereby a mixed fleece of uncrimped single filaments and filament groups is formed by a suitable aperture configuration of the spinning nozzles, whereby the single filaments of the fila-ment groups are bonded into heterogeneous multi-filaments by means of secondary bonding agents, at least over part of their length, in their mutually parallel position, and the multi-filaments and the single filaments are mixed in a random lay and bonded mutually, at least at their cross-over points.

10. A process according to claim 9, further characterized in that before the application of the secondary bonding medium that bonds the parallel filament groups into multi-filaments, the single filaments and the filament groups are pre-bonded by the use of additional single filaments that are spun on, by the application of heat and pressure.

11. A process according to either of claims 9 or 10, further characterized in that first the filaments in the filament groups are bonded into multi-filaments, and then the bonding of the single filaments, at least at their cross-over points, is effected with the help of thermoplastic bonding filaments.

12. A process according to claim 9, further characterized in that the textile is built up with the help of methylol groups of modified polybutyl acrylate-bonded polyester filaments into multi-filaments.

13. A process according to claim 12, further character-ized in that the bonding of the polyester filaments into multi-filaments takes place with the simultaneous use of methylolated melamine resins as bonding media.